Java Math Operators and Math Class Tutorial

In this tutorial, I will demonstrate how to perform the mathematic operations via the build-in Math operators and the Java Math class.

1. Introduction

Java language has provided a list of operator symbols to perform specific operations on one, two, or three operands and then returning a result. Java operators are generally used to manipulate primitive data types: boolean, byte, char, short, int, long, float and double. The Java operators are classified into eight different categories:

• assignment: =
• arithmetic: +, -, *, /, %, ++, and --
• relational: ==, !=, >, <, >=, and <=
• logical: &&, ||, and !
• bit-wise: &, |, and ^
• compound assignment: +=, -=, *=, /=, and %=
• conditional: ?:
• type comparison: instanceof

The Java Math class provides advanced mathematical calculations than what the math operators provide, such as square root of a number, etc.

In this example, I will demonstrate how to use these math operators and the java.lang.Math methods to perform the mathematics operations.

2. Technologies Used

The example code in this article was built and run using:

• Java 11
• Maven 3.3.9
• Eclipse Oxygen
• JUnit 4.12

3. Maven Project

3.1 Dependency

Add JUnit to the pom.xml.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>jcg.zheng.demo</groupId>
	<artifactId>java-math-demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<build>
		<sourceDirectory>src</sourceDirectory>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.8.0</version>
				<configuration>
					<release>11</release>
				</configuration>
			</plugin>
		</plugins>
	</build>
	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
		</dependency>
	</dependencies>
</project>

3.2 Java Object

I will create a POJO class which has only one String data member: name. It will be used to demonstrate the “==” and “!=” operators on an object.

POJO.java

package jcg.zheng.demo.data;

public class POJO {

	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

}

3.3 Java Object Has Equals Method

I will create a POJOHasEquals class which has equals and hashCode methods. It will be used to demonstrate the “==” operator and equals method on an object.

POJOHasEquals.java

package jcg.zheng.demo.data;

public class POJOHasEquals {

	private String name;

	public POJOHasEquals() {
		super();
	}

	public POJOHasEquals(String name) {
		super();
		this.name = name;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		POJOHasEquals other = (POJOHasEquals) obj;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}

	public String getName() {
		return name;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	public void setName(String name) {
		this.name = name;
	}

}

4. Arithmetic Operators

Java language provides the following arithmetic operators to operate on the primitive data types: int, byte, short, long, float, double.

The result’s data type is based on the operand with the higher precision. Here are the rules:

• If either operand is of type double, the other operand is converted to double and the result is also of type double.
• If either operand is of type float, the other operand is converted to float and the result is also of type float.
• If either operand is of type long, the other operand is converted to long and the result is also of type long.
• If either operand is of type int, the other operand is converted to int and the result is of type int.
• For all other cases, both operands are converted to int and the result is of type int.

4.1 Addition Operator

The “+” operator returns the sum of two numbers. In this step, I will create AddtionOperatorTest class which demonstrates how to add two numbers of type: int, byte, short, long, float, and double.

AdditionOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class AdditionOperatorTest {

	@Test
	public void byte_addition_arithmetic_operator() {
		byte b1 = 1;
		byte b2 = 2;

		byte sum = (byte) (b1 + b2);
		assertEquals(3, sum);

		// autoboxing
		Byte B1 = Byte.valueOf(b1);
		Byte B2 = Byte.valueOf(b2);
		assertEquals(3, B1 + B2);
	}

	@Test
	public void double_addition_arithmetic_operator() {
		double d1 = 10.01;
		double d2 = 20.05;

		double sum = d1 + d2;
		assertEquals(30.06, sum, 2);

		// autoboxing
		Double D1 = Double.valueOf(d1);
		Double D2 = Double.valueOf(d2);
		assertEquals(30.06, D1 + D2, 2);
	}

	@Test
	public void double_float() {
		double d = 12.234;
		float f = 10.1f;

		double sum = d + f;
		assertEquals(22.334, sum, 3);
	}

	@Test
	public void double_int() {
		double d = 12.234;
		int i = 10;

		double sum = d + i;
		assertEquals(22.234, sum, 3);
	}

	@Test
	public void float_addition_arithmetic_operator() {
		float num1 = 10.01f;
		float num2 = 20.05f;

		float sum = num1 + num2;
		assertEquals(30.06, sum, 2);

		// autoboxing
		Float F1 = Float.valueOf(num1);
		Float F2 = Float.valueOf(num2);
		assertEquals(30.06, F1 + F2, 2);
	}

	@Test
	public void float_int() {
		int i = 2;
		float f = 10.1f;

		float sum = i + f;
		assertEquals(12.1f, sum, 1);
	}

	@Test
	public void int_addition_arithmetic_operator() {
		int i = 10;
		int i2 = 20;

		int sum = i + i2;
		assertEquals(30, sum);

		Integer num1 = Integer.valueOf(i);
		Integer num2 = Integer.valueOf(i2);

		assertEquals(30, num1 + num2);
	}

	@Test
	public void long_addition_arithmetic_operator() {
		long num1 = 10;
		long num2 = 20;

		long sum = num1 + num2;
		assertEquals(30, sum);

		Long L1 = Long.valueOf(num1);
		Long L2 = Long.valueOf(num2);

		assertEquals(30, L1 + L2);
	}

	@Test
	public void long_int() {
		int i = 2;
		long l = 10000l;

		long sum = i + l;
		assertEquals(10002l, sum);
	}

	@Test
	public void short_addition_arithmetic_operator() {
		short s1 = 1;
		short s2 = 2;

		short sum = (short) (s1 + s2);
		assertEquals(3, sum);
	}

	@Test
	public void byte_add_constants() {
		byte sum = 1 + 2;
		// the operands 1 and 2 are constants.
		// the compiler computes the sum and replaces 1+2 as 3.
		assertEquals(3, sum);
	}

	@Test
	public void shorthand() {
		int i = 10;
		i += 7;

		assertEquals(17, i);
	}

}

Note: at line 14, 120, the “+” operator returns a result of int type because operands are byte and short.

Execute mvn test -Dtest=AdditionOperatorTest and capture the output.

Junit Output

Running jcg.zheng.demo.mathoperator.arithmetic.AdditionOperatorTest
Tests run: 12, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.109 sec

Results :

Tests run: 12, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.579 s
[INFO] Finished at: 2019-09-01T16:32:01-05:00
[INFO] ------------------------------------------------------------------------

C:\MaryZheng\Workspaces\jdk12\java-math-demo>

4.2 Subtraction Operator

The “-“ operator returns the difference of two numbers. In this step, I will create SubtractionOperatorTest class to demonstrate the “-” operator usages for the primitive data types: int, byte, short, long, float, and double .

SubtractionOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class SubtractionOperatorTest {

	@Test
	public void byte_subtraction_arithmetic_operator() {
		byte num1 = 3;
		byte num2 = 2;

		byte diff = (byte) (num1 - num2);
		assertEquals(1, diff);
	}

	@Test
	public void byte_subtraction_arithmetic_operator_2() {
		byte num1 = 1;
		byte num2 = 2;

		byte diff = (byte) (num1 - num2);
		assertEquals(-1, diff);
	}

	@Test
	public void double_subtraction_arithmetic_operator() {
		double num1 = 40.09;
		double num2 = 20.05;

		double diff = num1 - num2;
		assertEquals(20.04, diff, 2);
	}

	@Test
	public void double_float() {
		double d = 12.234;
		float f = 10.1f;

		double diff = d - f;
		assertEquals(2.134, diff, 3);
	}

	@Test
	public void double_int() {
		double d = 12.234;
		int i = 10;

		double diff = d - i;
		assertEquals(2.234, diff, 3);
	}

	@Test
	public void float_subtraction_arithmetic_operator() {
		float num1 = 10.08f;
		float num2 = 20.05f;

		float diff = num1 - num2;
		assertEquals(-10.03, diff, 2);
	}

	@Test
	public void float_int() {
		int i = 20;
		float f = 10.1f;

		float diff = i - f;
		assertEquals(9.1f, diff, 1);
	}

	@Test
	public void int_subtraction_arithmetic_operator() {
		int i = 10;
		int i2 = 20;

		int diff = i - i2;
		assertEquals(-10, diff);
	}

	@Test
	public void long_subtraction_arithmetic_operator() {
		long num1 = 10;
		long num2 = 20;

		long diff = num1 - num2;
		assertEquals(-10, diff);
	}

	@Test
	public void long_int() {
		int i = 2;
		long l = 10000l;

		long diff = l - i;
		assertEquals(9998l, diff);
	}

	@Test
	public void short_subtraction_arithmetic_operator() {
		short num1 = 1;
		short num2 = 2;

		short diff = (short) (num1 - num2);
		assertEquals(-1, diff);
	}

	@Test
	public void byte_add_constants() {
		byte diff = 3 - 2;
		assertEquals(1, diff);
	}

	@Test
	public void shorthand() {
		int i = 10;
		i -= 7;

		assertEquals(3, i);
	}

	@Test
	public void test_Integer() {
		Integer num1 = Integer.valueOf(5);
		Integer num2 = Integer.valueOf(6);

		assertEquals(-1, num1 - num2);
	}

}

Execute mvn test -Dtest=SubtractionOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.arithmetic.SubtractionOperatorTest
Tests run: 14, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.135 sec

Results :

Tests run: 14, Failures: 0, Errors: 0, Skipped: 0

4.3 Increment Operator

The “++” operator increases the value by 1 for primitive data types: int, byte, short, long, float, and double. It can be used in front of a variable or after it.

• ++x : increments x and read the value of x afterwards
• x++ : increments x and read the value of x beforehand

In this step, I will demonstrate the “++” operator usages with Junit test cases.

Note:

• line 15 – the variable j has the variable x‘s old value because of x++.
• line 24 – the variable j has the variable x‘s new value because of ++x

IncrementOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;


public class IncrementOperatorTest {

	@Test
	public void test_increment_post() {
		int i = 0;
		int j = i++;
		assertEquals(1, i);
		assertEquals(0, j);

	}

	@Test
	public void test_increment_pre() {
		int i = 0;
		int j = ++i;
		assertEquals(1, i);
		assertEquals(1, j);

	}

	@Test
	public void byte_increment_arithmetic_operator() {
		byte b = 1;
		b++;

		assertEquals(2, b);
	}

	@Test
	public void double_increment_arithmetic_operator() {
		double d = 10.01;
		d++;

		assertEquals(11.01, d, 2);
	}

	@Test
	public void float_increment_arithmetic_operator() {
		float f = 10.01f;

		f++;

		assertEquals(11.01, f, 2);
	}

	@Test
	public void int_increment_arithmetic_operator() {
		int i = 10;

		i++;
		assertEquals(11, i);
	}

	@Test
	public void long_increment_arithmetic_operator() {
		long l = 10;
		l++;

		assertEquals(11, l);
	}

	@Test
	public void short_increment_arithmetic_operator() {
		short s = 1;
		s++;

		assertEquals(2, s);
	}

}

Execute mvn test -Dtest=IncrementOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.arithmetic.IncrementOperatorTest
Tests run: 8, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.121 sec

Results :

Tests run: 8, Failures: 0, Errors: 0, Skipped: 0

4.4 Decrement Operator

The “–” operator returns the number by subtracting 1 from it. It also can be used in front of or after a variable (int, byte, short, long, float, double).

• --x: decrements x and read the value of x afterwards
• x--: decrements x and read the value of x beforehand

In this step, I will demonstrate the “–” operator usages with Junit test cases. Please verify the highlighted assertion statements.

DecrementOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;


public class DecrementOperatorTest {

	@Test
	public void test_decrement_post() {
		int i = 0;
		int j = i--;
		assertEquals(-1, i);
		assertEquals(0, j);

	}

	@Test
	public void test_decrement_pre() {
		int i = 0;
		int j = --i;
		assertEquals(-1, i);
		assertEquals(-1, j);

	}

	@Test
	public void byte_decrement_arithmetic_operator() {
		byte b = 1;
		b--;

		assertEquals(0, b);
	}

	@Test
	public void double_decrement_arithmetic_operator() {
		double d = 10.01;
		d--;

		assertEquals(9.01, d, 2);
	}

	@Test
	public void float_decrement_arithmetic_operator() {
		float f = 10.01f;
		f--;

		assertEquals(9.01, f, 2);
	}

	@Test
	public void int_decrement_arithmetic_operator() {
		int i = 10;
		i--;

		assertEquals(9, i);
	}

	@Test
	public void long_decrement_arithmetic_operator() {
		long l = 10;
		l--;

		assertEquals(9, l);
	}

	@Test
	public void short_decrement_arithmetic_operator() {
		short s = 1;
		s--;

		assertEquals(0, s);
	}

}

Execute mvn test -Dtest=DecrementOperatorTest and capture the output.

Junit Output

Running jcg.zheng.demo.mathoperator.arithmetic.DecrementOperatorTest
Tests run: 8, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.106 sec

Results :

Tests run: 8, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.158 s
[INFO] Finished at: 2019-09-01T16:35:06-05:00
[INFO] ------------------------------------------------------------------------

C:\MaryZheng\Workspaces\jdk12\java-math-demo>

4.5 Multiplication Operator

The “*” operator returns the product of two numbers. In this step, I will demonstrate the “*” operator usages with Junit test cases:

MultiplicationOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;


public class MultiplicationOperatorTest {

	@Test
	public void byte_multiplication_arithmetic_operator() {
		byte num1 = 1;
		byte num2 = 2;

		byte product = (byte) (num1 * num2);
		assertEquals(2, product);
	}

	@Test
	public void double_multiplication_arithmetic_operator() {
		double num1 = 10.01;
		double num2 = 20.05;

		double product = num1 * num2;
		assertEquals(200.71, product, 2);
	}

	@Test
	public void double_float() {
		double d = 12.234;
		float f = 10.1f;
		
		double product = d * f;
		assertEquals(123.563, product, 3);
	}

	@Test
	public void double_int() {
		double d = 12.234;
		int i = 10;
		
		double product = d * i;
		assertEquals(122.234, product, 3);
	}

	@Test
	public void float_multiplication_arithmetic_operator() {
		float num1 = 10.01f;
		float num2 = 20.05f;

		float product = num1 * num2;
		assertEquals(200.71, product, 2);
	}

	@Test
	public void float_int() {
		int i = 2;
		float f = 10.1f;
		
		float product = i * f;
		assertEquals(20.2f, product, 1);
	}

	@Test
	public void int_multiplication_arithmetic_operator() {
		int i = 10;
		int i2 = 20;

		int product = i * i2;
		assertEquals(200, product);
	}
	
	@Test
	public void long_multiplication_arithmetic_operator() {
		long num1 = 10;
		long num2 = 20;

		long product = num1 * num2;
		assertEquals(200, product);
	}
	
	@Test
	public void long_int() {
		int i = 2;
		long l = 10000l;
		
		long product = i * l;
		assertEquals(20000l, product);
	}
	
	@Test
	public void short_multiplication_arithmetic_operator() {
		short num1 = 1;
		short num2 = 2;

		short product = (short) (num1 * num2);
		assertEquals(2, product);
	}
	
	@Test
	public void byte_add_constants() {
		byte product = 1 * 2;
		//the operands 1 and 2 are compile time constants. Therefore, the compiler computes the product as compile time and replaces 1*2 as 3.
		assertEquals(2, product);
	}
	
	@Test
	public void shorthand() {
		int i = 10;
		i *= 7;
		
		assertEquals(70, i);
	}
	
	@Test
	public void test_Integer() {
		Integer num1 = Integer.valueOf(5);
		Integer num2 = Integer.valueOf(6);
	 
		assertEquals(30, num1 * num2);
	}

}

Execute mvn test -Dtest=MultiplicationOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.arithmetic.MultiplicationOperatorTest
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.12 sec

Results :

Tests run: 13, Failures: 0, Errors: 0, Skipped: 0

4.6 Division Operator

The “/” operator returns the quotient when performing the division on the two numbers. In this step, I will demonstrate the “/” operator usages with Junit test cases:

Note: the “/” operator does the integer division, so the remainder is thrown away. See highlighted statements as examples.

DivisionOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class DivisionOperatorTest {

	@Test
	public void byte_division_arithmetic_operator() {
		byte num1 = 4;
		byte num2 = 2;

		byte division = (byte) (num1 / num2);
		assertEquals(2, division);
	}

	@Test
	public void byte_division_arithmetic_operator_2() {
		byte num1 = 4;
		byte num2 = 3;

		byte division = (byte) (num1 / num2);
		assertEquals(1, division);
	}

	@Test
	public void byte_division_arithmetic_operator_3() {
		byte num1 = 3;
		byte num2 = 4;

		byte division = (byte) (num1 / num2);
		assertEquals(0, division);
	}

	@Test
	public void double_division_arithmetic_operator() {
		double num1 = 10.02;
		double num2 = 3;

		double division = num1 / num2;
		assertEquals(3.34, division, 2);
	}

	@Test
	public void double_float() {
		double d = 12.234;
		float f = 10f;

		double division = d / f;
		assertEquals(1.223, division, 3);
	}

	@Test
	public void double_int() {
		double d = 12.234;
		int i = 10;

		double division = d / i;
		assertEquals(1.223, division, 3);
	}

	@Test
	public void float_division_arithmetic_operator() {
		float num1 = 10.02f;
		float num2 = 2f;

		float division = num1 / num2;
		assertEquals(5.01, division, 2);
	}

	@Test
	public void float_int() {
		int i = 2;
		float f = 10.1f;

		float division = f / i;
		assertEquals(5.05f, division, 2);
	}

	@Test
	public void int_division_arithmetic_operator() {
		int i = 40;
		int i2 = 20;

		int division = i / i2;
		assertEquals(2, division);
	}

	@Test
	public void long_division_arithmetic_operator() {
		long num1 = 60;
		long num2 = 20;

		long division = num1 / num2;
		assertEquals(3, division);
	}

	@Test
	public void long_int() {
		int i = 2;
		long l = 10000l;

		long division = l / i;
		assertEquals(5000l, division);
	}

	@Test
	public void short_division_arithmetic_operator() {
		short num1 = 1;
		short num2 = 2;

		short division = (short) (num1 / num2);
		assertEquals(0, division);
	}

	@Test
	public void byte_add_constants() {
		byte division = 1 / 2;
		assertEquals(0, division);
	}

	@Test
	public void shorthand() {
		int i = 10;
		i /= 2;

		assertEquals(5, i);
	}

	@Test
	public void test_Integer() {
		Integer num1 = Integer.valueOf(13);
		Integer num2 = Integer.valueOf(6);

		assertEquals(2, num1 / num2);
	}
}

Execute mvn test -Dtest=DivisionOperatorTest and capture the output.

Junit Output

Running jcg.zheng.demo.mathoperator.arithmetic.DivisionOperatorTest
Tests run: 15, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.112 sec

Results :

Tests run: 15, Failures: 0, Errors: 0, Skipped: 0

4.7 Remainder Operator

The “%” operator returns the remainder of two numbers after performing division on two numbers. In this step, I will demonstrate the “%” operator usages with Junit test cases:

RemainderOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;

import org.junit.Test;


public class RemainderOperatorTest {

	@Test
	public void byte_remainer_arithmetic_operator() {
		byte num1 = 1;
		byte num2 = 2;

		byte remainer = (byte) (num1 % num2);
		assertEquals(1, remainer);
	}

	@Test
	public void double_remainer_arithmetic_operator() {
		double num1 = 21;
		double num2 = 5;

		double remainer = num1 % num2;
		assertEquals(1, remainer, 2);
	}

	@Test
	public void double_float() {
		double d = 14;
		float f = 3f;

		double remainer = d % f;
		assertEquals(2, remainer, 0);
	}

	@Test
	public void double_int() {
		double d = 12.234;
		int i = 10;

		double remainer = d % i;
		assertEquals(2.234, remainer, 3);
	}

	@Test
	public void float_remainer_arithmetic_operator() {
		float num1 = 100f;
		float num2 = 20f;

		float remainer = num1 % num2;
		assertEquals(0, remainer, 2);
	}

	@Test
	public void float_int() {
		int i = 2;
		float f = 10.1f;

		float remainer = i % f;
		assertEquals(2f, remainer, 1);
	}

	@Test
	public void int_remainer_arithmetic_operator() {
		int i = 10;
		int i2 = 20;

		int remainer = i % i2;
		assertEquals(10, remainer);
	}

	@Test
	public void long_remainer_arithmetic_operator() {
		long num1 = 10;
		long num2 = 20;

		long remainer = num1 % num2;
		assertEquals(10, remainer);
	}

	@Test
	public void long_int() {
		int i = 2;
		long l = 10000l;

		long remainer = i % l;
		assertEquals(2, remainer);
	}

	@Test
	public void short_remainer_arithmetic_operator() {
		short num1 = 1;
		short num2 = 2;

		short remainer = (short) (num1 % num2);
		assertEquals(1, remainer);
	}

	@Test
	public void byte_add_constants() {
		byte remainer = 1 % 2;
		assertEquals(1, remainer);
	}

	@Test
	public void shorthand() {
		int i = 10;
		i %= 7;

		assertEquals(3, i);
	}
	
	@Test
	public void test_Integer() {
		Integer num1 = Integer.valueOf(5);
		Integer num2 = Integer.valueOf(6);
	 
		assertEquals(5, num1 % num2);
	}

}

Execute mvn test -Dtest=RemainderOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.arithmetic.RemainderOperatorTest
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.112 sec

Results :

Tests run: 13, Failures: 0, Errors: 0, Skipped: 0

4.8 Ternary Operator

The ternary operator consists of a condition that evaluates to either true or false, plus a value that is returned if the condition is true and another value that is returned if the condition is false.

In this step, I will demonstrate the “?:” operator usages with Junit test cases.

TernaryOperatorTest.java

package jcg.zheng.demo.mathoperator.arithmetic;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Test;

public class TernaryOperatorTest {

	@Test
	public void test_ternary() {
		assertTrue(allowToDrink(29));
		assertEquals("Enjoying", greetingMsgDrink(28));
		assertFalse(allowToDrink(20));
	}

	private boolean allowToDrink(int age) {
		boolean meetMLDA = (age >= 21) ? true : false;
		return meetMLDA;
	}
	
	private String greetingMsgDrink(int age) {
		String meetMLDA = (age >= 21) ? "Enjoying" : "Please wait until you are 21.";
		return meetMLDA;
	}
}

Execute mvn test -Dtest=TernaryOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.arithmetic.TernaryOperatorTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.121 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

5. Relational Operators

Java language provides the following relational operators to return a boolean value when comparing two operands belong to the primitive data type.

5.1 Equals Operator

The “==” operator returns the memory address comparison with two variables. In this step, I will demonstrate the following user cases:

• line 69 , 70: two String literals refer to the same object, so both "==" and equals return true.
• line 77, 85 : “==” return false when comparing two new instances of POJO and POJOHasEquals
• line 78: “equals” return false when comparing two new instances of POJO
• line 86: “equals” returns true when comparing two new instances of POJOHasEquals.

EqualsOperatorTest.java

package jcg.zheng.demo.mathoperator.relational;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Test;

import jcg.zheng.demo.data.POJO;
import jcg.zheng.demo.data.POJOHasEquals;

public class EqualsOperatorTest {

	@Test
	public void same_int_value_should_equalsto_eachother() {
		int i1 = 2;
		int i2 = 2;
		assertTrue(i1 == i2);
		assertFalse(i2 == 1);

		Integer num1 = Integer.valueOf(i1);
		Integer num2 = Integer.valueOf(i2);
		assertTrue(num1 == num2);
	}

	@Test
	public void same_byte_value_should_equalsto_eachother() {
		byte i1 = 2;
		byte i2 = 2;
		assertTrue(i1 == i2);
		assertFalse(i2 == 1);
	}

	@Test
	public void same_short_value_should_equalsto_eachother() {
		short i1 = 2;
		short i2 = 2;
		assertTrue(i1 == i2);
		assertFalse(i2 == 1);
	}

	@Test
	public void same_long_value_should_equalsto_eachother() {
		long i1 = 2;
		long i2 = 2;
		assertTrue(i1 == i2);
		assertFalse(i2 == 1);
	}

	@Test
	public void same_float_value_should_equalsto_eachother() {
		float i1 = 2.3f;
		float i2 = 2.3f;
		assertTrue(i1 == i2);

	}

	@Test
	public void same_double_value_should_equalsto_eachother() {
		double i1 = 20.0;
		double i2 = 20.00;
		assertTrue(i1 == i2);

	}

	@Test
	public void same_String_value_should_equalsto_eachother() {
		String s1 = "Mary";
		String s2 = "Mary";
		assertTrue(s1 == s2);
		assertTrue(s1.equals(s2));
	}

	@Test
	public void same_new_instance_of_POJO_not_equalsto_eachother() {
		POJO p1 = new POJO();
		POJO p2 = new POJO();
		assertFalse(p1 == p2);
		assertFalse(p1.equals(p2));
	}

	@Test
	public void same_new_instance_of_POJOHasEquals_not_equalsto_eachother() {
		POJOHasEquals p1 = new POJOHasEquals("Mary");
		POJOHasEquals p2 = new POJOHasEquals("Mary");
		assertFalse(p1 == p2);
		// Note because the overwrite equals. these two object return true from equals()
		assertTrue(p1.equals(p2));
	}
}

Execute mvn test -Dtest=EqualsOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.relational.EqualsOperatorTest
Tests run: 9, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.116 sec

Results :

Tests run: 9, Failures: 0, Errors: 0, Skipped: 0

5.2 Not Equal Operator

The “!=” operator is the counterpart of the “==” operator. In this step, I will demonstrate with Junit test class.

Note:

• line 70: two String literals refer to the same object, so "!=" returns false.
• line 74 : “!=” return true when comparing literal String to the new String
• line 82: “!=” return true when comparing two new instances of POJO from default constructor
• line 90: “!=” returns true when comparing two new instances of POJOHasEquals.

NotEqualsOperatorTest.java

package jcg.zheng.demo.mathoperator.relational;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Test;

import jcg.zheng.demo.data.POJO;
import jcg.zheng.demo.data.POJOHasEquals;

public class NotEqualsOperatorTest {

	@Test
	public void same_int_resutls_false_for_notequalsto_operator() {
		int i1 = 2;
		int i2 = 2;
		assertFalse(i1 != i2);
		assertFalse(i2 != 2);

		Integer num1 = Integer.valueOf(i1);
		Integer num2 = Integer.valueOf(i2);
		assertFalse(num1 != num2);
	}

	@Test
	public void same_byte_resutls_false_for_notequalsto_operator() {
		byte i1 = 2;
		byte i2 = 2;
		assertFalse(i1 != i2);
		assertTrue(i2 != 1);
	}

	@Test
	public void same_short_resutls_false_for_notequalsto_operator() {
		short i1 = 2;
		short i2 = 2;
		assertFalse(i1 != i2);
		assertTrue(i2 != 1);
	}

	@Test
	public void same_long_resutls_false_for_notequalsto_operator() {
		long i1 = 2;
		long i2 = 2;
		assertFalse(i1 != i2);
		assertTrue(i2 != 1);
	}

	@Test
	public void same_float_resutls_false_for_notequalsto_operator() {
		float i1 = 2.3f;
		float i2 = 2.3f;
		assertFalse(i1 != i2);

	}

	@Test
	public void same_double_resutls_false_for_notequalsto_operator() {
		double i1 = 20.0;
		double i2 = 20.00;
		assertFalse(i1 != i2);

	}

	@Test
	public void same_literal_String_resutls_false() {
		//liternal String are same if the values are same
		String s1 = "Mary";
		String s2 = "Mary";
		assertFalse(s1 != s2);
		
		//s3 uses new keyword, it will have a new instance
		String s3 = new String("Mary");
		assertTrue(s1 != s3);

	}

	@Test
	public void test_notequaltoOperator_POJO() {
		POJO p1 = new POJO();
		POJO p2 = new POJO();
		assertTrue(p1 != p2);

	}

	@Test
	public void test_notequaltoOperator_POJOHasEquals_default() {
		POJOHasEquals p1 = new POJOHasEquals();
		POJOHasEquals p2 = new POJOHasEquals();
		assertTrue(p1 != p2);

	}

	@Test
	public void test_notequaltoOperator_POJOHasEquals() {
		POJOHasEquals p1 = new POJOHasEquals("Mary");
		POJOHasEquals p2 = new POJOHasEquals("Mary");
		assertTrue(p1 != p2);
	}
}

Execute mvn test -Dtest=NotEqualsOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.mathoperator.relational.NotEqualsOperatorTest
Tests run: 10, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.128 sec

Results :

Tests run: 10, Failures: 0, Errors: 0, Skipped: 0

6. String Operator

The “+” operator is used to concatenate string. In this step, I will demonstrate several ways to use it:

• Both operands are String variables
• Only one operand is String variable, the other is a primitive type
• Only one operand is String variable, the other is a constant

StringOperatorTest.java

package jcg.zheng.demo;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;

import org.junit.Test;

public class StringOperatorTest {

	@Test
	public void addition_concatenate_operator() {
		String msg1 = "Hello";
		String msg2 = " World!";

		assertEquals("Hello World!", msg1 + msg2);
	}

	@Test
	public void addition_concatenate_operator_hybrid() {
		int num = 10;
		String msg = "Hello ";
		assertEquals("Hello 10", msg + num);
	}

	@Test
	public void addition_concatenate_operator_hybrid_2() {
		String numStr = "10.00";
		String msg = "10.00 ";
		assertEquals("10.00 10.00", msg + numStr);
	}

	@Test
	public void mixer_constant() {
		//1, 2, 3 are constants
		assertEquals(6, 1 + 2 + 3);
		
		int one = 1;
		String three = "3";
		
		// 2 is the constant, so one+2 is 3
		assertEquals("33", one + 2 + three);
		assertNotEquals("123", one + 2 + three);
		assertEquals(6, 1 + 2 + 3);
	}

	@Test
	public void with_null() {
		String str1 = "Hello";
		String str2 = null;

		assertEquals("Hellonull", (str1 + str2)); // String str2 is null, the compiler replaces it will string “null”.
		assertNotEquals("Hello", str1 + str2);
	}

	@Test
	public void with_boolean() {
		String msg = "Hello world!";
		assertEquals("Hello world!true", msg + true);
		assertEquals("Hello world!false", msg + false);
	}
}

Note:

• line 41: variable one is type of int, it first evaluates with constant 2 to get value 3, then concatenates with variable three, so the final result is “33”
• line 51 – a null object displays as null
• line 58 – a boolean variable of true displays as true
• line 59 – a boolean variable of false displays as false

Execute mvn test -Dtest=StringOperatorTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.StringOperatorTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.181 sec

Results :

Tests run: 6, Failures: 0, Errors: 0, Skipped: 0

7. Operator Precedence

The Java math operators have a natural operator precedence which is same as the precedence of standard math operators.

The math operators * and / for multiplication and division take precedence over the + and - operators. That means, that multiplications and divisions are evaluated before addition and subtraction in math expressions. In case there are multiple * and / operators they will be calculated from left to right.

In this step, I will create a Junit test to show the order of precedence.

OperatorPrecedenceTest.java

package jcg.zheng.demo;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class OperatorPrecedenceTest {

	@Test
	public void parentheses_is_first() {
		int result = 100 * 100 / 5 + 200 * 3 / 2 + 6 * (4 % 5);
		assertEquals(2324, result);
	}

	@Test
	public void test_OperatorPrecedence() {
		int result = 100 / 5 * 100 + 200 * 3 / 2 + 6 * 4 % 5;
		assertEquals(2304, result);
	}

	@Test
	public void from_left_to_right() {
		int cal = 1 * 9 % 8 * 3 * 5 / 3;
		assertEquals(5, cal);
	}

	@Test
	public void addion_yields() {
		int cal = 6 + 3 * 5 / 3;
		assertEquals(11, cal);
	}

	@Test
	public void minus_yields() {
		int cal = 6 - 3 * 5 % 3;
		assertEquals(6, cal);
	}

}

Execute mvn test -Dtest=OperatorPrecedenceTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.OperatorPrecedenceTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.24 sec

Results :

Tests run: 5, Failures: 0, Errors: 0, Skipped: 0

8. Java Math Class

The Java Math class provides static methods to perform more advanced mathematical calculations than what the basic Java math operators provide.

In this step, I will create a Junit test class to demonstrate advanced calculation methods:

• abs – returns the absolute value of the argument
• floor – returns the largest value based on the arguments
• ceil – returns the smallest value based on the arguments
• min – returns the smaller of two values
• max – returns the larger of two values
• pow – returns the value of the first argument raised to the power of the second argument
• log10 – returns the base 10 logarithm of a double value
• sqrt – returns the correctly rounded positive square root of a double value

MathStaticMethodsTest.java

package jcg.zheng.demo;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class MathStaticMethodsTest {

	@Test
	public void test_abs() {
		assertEquals(10, Math.abs(10));

		assertEquals(20, Math.abs(-20));
	}

	@Test
	public void test_ceil() {
		assertEquals(8.0, Math.ceil(7.343), 0);
	}

	@Test
	public void test_floor() {
		assertEquals(7.0, Math.floor(7.343), 0);
	}

	@Test
	public void test_min() {
		assertEquals(8, Math.min(8, 17.343), 0);
	}

	@Test
	public void test_max() {
		assertEquals(17.343, Math.max(8, 17.343), 0);
	}

	@Test
	public void test_pow() {
		assertEquals(9, Math.pow(3, 2), 0);
	}

	@Test
	public void test_pi() {
		double area = Math.floor(Math.PI * Math.pow(10, 2));
		assertEquals(314, area, 0);
	}


	@Test
	public void test_sqrt() {
		double sroot = Math.sqrt(16);
		assertEquals(4, sroot, 0);
	}

	@Test
	public void test_log10() {
		double logV = Math.log10(100);
		assertEquals(2, logV, 0);
	}

	@Test
	public void test_sin() {
		assertEquals(0.5, Math.sin(60), 1);
	}

	@Test
	public void test_cos() {
		assertEquals(0.5, Math.cos(30), 1);
	}

	@Test
	public void test_log() {
		assertEquals(1, Math.log(Math.E), 0);
		assertEquals(2, Math.log(Math.pow(Math.E, 2)), 0);
		assertEquals(2, Math.log(Math.exp(2)), 0);
	}

	@Test
	public void test_constants() {
		System.out.println("Pi=" + Math.PI);
		System.out.println("E=" + Math.E);
	}

	@Test
	public void test_exp() {
		assertEquals(2, Math.log(Math.exp(2)), 0);
	}
}

Execute mvn test -Dtest=MathStaticMethodsTest and capture the output.

Junit Output

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.MathStaticMethodsTest
Pi=3.141592653589793
E=2.718281828459045
Tests run: 14, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.122 sec

Results :

Tests run: 14, Failures: 0, Errors: 0, Skipped: 0

9. Summary

In this example, I demonstrated how to use the build-in math operators and Math static methods to perform arithmetic, relational, and other advanced mathematics operations.

10. Download the Source Code

This example consists of a Maven project which uses Math class and built-in Math operators.

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